嚼烟习俗地区的牙釉质电子自旋共振剂量学的研究

目的 研究嚼烟习俗对牙釉质电子自旋共振(ESR)剂量学的影响。方法 用机械方法获得20个孟买地区的舌侧牙釉质样品与10个混合均匀的日本人舌侧牙釉质样品。用⁶⁰Co γ射线分别照射部分牙釉质样品,使用ESR波谱仪测量辐射前和不同辐射剂量后牙釉质样品的ESR信号。结果 9个孟买牙釉质样品,其ESR的本底信号强度明显高于日本人的平均水平,为日本人水平的1.5~3.3倍。ESR本底信号强度较高的样品,γ射线照射后,剂量学信号的辐射响应略低,说明高本底可能降低了辐射剂量的灵敏度。6个样品辐射响应的平均值为(0.42±0.03)mGy,与日本牙釉质混合样品很相近。结论 嚼烟地区的部分牙釉质的ESR本底水平明显高于一般平均水平,可能是嚼烟中大量的烟碱与牙釉质相互作用的结果。进一步研究特殊生活习俗对牙釉质ESR剂量学的影响,有助于提高不同地区剂量重建的精度,为正确地评价辐射事故剂量提供科学依据。     

牙釉质电子自旋共振剂量学的本底拟合扣除法研究

牙釉质ESR剂量学近年来得到了广泛的应用。然而，牙釉质中含有一定量的有机物，其ESR信号对射线不敏感，称之为本底信号。由于本底信号很宽，基本上覆盖了低剂量范围（约几百mGy）的剂量学信号，而一般情况下的事故剂量大多不超过1Gy，因此如何减少本底的影响，较准确地估算出受照射剂量，一直是ESR剂量学的一个重要课题。目前进行剂量重建的方法主要有附加照射法、部分刻度法和刻度曲线法。其中刻度曲线法由于大大节省了图谱处理时间且对样品没有破坏性而受到广泛关注。但是该方法是基于辐射灵敏度的个体差异很小的这样一个假设。     

山羊牙釉质电子自旋共振的剂量学特性

目的 探讨山羊牙釉质电子自旋共振(ESR)的剂量学的特性.方法 采用机械和化学处理相结合的方法,制备5组不同年龄的山羊牙釉质样品.用137 Cs γ射线照射山羊牙釉质样品,使用ESR波谱仪测量辐射前和不同辐射剂量后不同牙釉质样品的ESR信号.结果 137Cs γ射线照射前,山羊牙釉质所固有的ESR本底信号平均值为21.5,明显低于人的平均本底强度水平39.5;与人牙釉质相同,山羊牙釉质照射后产生的剂量学信号的强度与照射剂量线性相关,5组100 mg山羊牙釉质样品,其剂量学峰的辐射灵敏度的平均值为(34.3±1.9)/Gy,与人牙釉质样品的辐射响应平均值36.3/Gy非常接近.结论 人类牙釉质样品缺乏时,可以用相同辐射环境中的山羊牙釉质作为替代品进行剂量重建,为正确地评价辐射事故剂量提供科学依据.

Abstract：

Objectlve To study the properties of goat tooth enamel electron spin resonance (ESR)dosimetry.Methods Tootll enamel samples of goats were achieved by combined mechanical and chemical treatment at the ages of l,2,3,5,and 6 years.respectively and 9 enamel samples of adult molar were obtained.These enamel samples were exposed to 137Cs γ-rays at the cumulative doses of 0,0.5,1.0,2.0,and 5.0 Gy,respectively.ESR spectra Was measured before and after exposure.Results The background signal of goat tooth samples W88 21.5,significantly lower than that of the adult molar samples(39.5).The dusimetric signal intensity of the goat enamel increased with the radiation dose in a linear manner just as that of the human molars.The average radiation sensitivity of the goat tooth samples was(34.3±1.9)/Gy,close to that of the human tooth samples.Conclusions Goat teeth can be used for retrospective radiation dose reconstruction when human teeth are unavailable,in order to previde scientific data for dose reconstruction accurately.     

不同制备方法对牙釉质样品ESR信号的影响

目的研究不同制备方法对牙釉质样品ESR信号的影响，有效地提高牙釉质样品ESR剂量学的灵敏度。方法对无放射线照射史成年人臼齿分别用化学、机械以及机械加化学方法进行处理，制备牙釉质样品。利用电子自旋共振仪测定不同制备方法处理的样品在^60Coγ射线照射不同剂量后的ESR信号。比较分析其灵敏度，从而寻求一种对牙釉质样品ESR信号影响较小的样品制备及处理方法。结果不同方法处理的牙釉质样品的ESR信号，对^60Coγ射线的响应有较明显的差异。结论利用牙釉质ESR剂量学重建受照人员剂量时，尤其是使用附加照射法进行较低剂量重建时，选择合适的样品制备方法是十分重要的。     

呼和浩特市城区表层土壤和环境辐射水平调查

目的 测定呼和浩特市城区表层土壤中天然和人工放射性核素比活度,测量环境放射性水平,评估其对居民产生的健康风险。方法 采用高纯锗γ能谱仪对呼和浩特市城区48个表层土壤样品进行了放射性核素的测定;用环境γ剂量率仪测量了环境辐射水平;与世界和我国土壤中放射性核素比活度平均值进行了比较,通过联合国原子辐射影响科学委员会和相关文献推荐的方法估算了居民受照剂量。结果 呼和浩特市表层土壤样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs的比活度平均值分别为（29.29±12.95）、（39.33±4.34）、（29.77±3.21）、（650.49±62.21）、（1.62±1.53） Bq/kg;测量的空气吸收剂量率均值为（86.32±11.92） nGy/h,该地区居民受到室外γ辐射所致年有效剂量为79.27 μSv/年。结论 呼和浩特市表层土壤中天然放射性核素比活度和环境辐射处于正常本底水平,对居民造成的健康风险非常低。     

辐射诱导双基因质粒pEgr-1-endostatin-TNF-α的抗肿瘤作用研究

目的 探讨放射线诱导重组质粒pEgr-1-endostatin-TNF-α在小鼠体内的表达及其与射线协同抗肿瘤效应。方法 Lewis肺癌荷瘤鼠240只,随机分为4组:对照组、照射组、质粒组、质粒+照射组。将重组质粒pEgr-1-endostatin-TNF-α注射到荷瘤鼠肿瘤内,24 h后对质粒+照射组采用γ射线肿瘤局部照射10 Gy,诱导目的基因表达,ELISA法测定小鼠不同时间血清中的内皮抑素及TNF-α浓度,免疫组织化学染色检测肿瘤组织中血管内皮细胞CD31的表达,与HE染色分别计算肿瘤血管密度,测量肿瘤大小,观察肿瘤生长情况。结果 质粒+照射组内皮抑素及TNF-α表达量明显增加,第2周表达量达到高峰,分别为(52.64±4.19)和(12.01±0.87)ng/ml,持续到第4周仍有较高浓度表达,与其他3组比较差异有统计学意义(F=29.726,P<0.05)。质粒+对照组HE染色肿瘤组织血管密度较对照组明显减少[(4.7±0.8)与(10.0±1.2)个/视野, t=14.063, P<0.05],肿瘤生长较对照组和照射组受到明显抑制[(5907.2±78.6)、(4653.4±32.8)和(763.5±12.3) mm³, F=16.415,P <0.05)]。结论 重组质粒pEgr-1-endostatin-TNF-α可以通过射线的诱导在小鼠体内表达,与单纯放疗相比较表现出明显的抑制肿瘤血管形成和控制肿瘤生长的作用。     

高本底地区环境辐射和累积照射量的测定

本文报道了广东高本底地区调查第二阶段环境辐射和累积照射量的测定结果.根据用国产FD-71型晶体管小型闪烁辐射仪测得环境γ照射量率的结果.估算高本底地区居民所受γ外照射年平均照射量为510+60mR,对照地区为142+19mR.使用LiF(Mg: Ti)-M和CaSO₄(Tm)热释光剂量元件测量了环境及人体γ累积照射量,两种元件测得的结果比较一致.根据LiF(Mg: Ti)-M测得数据推算.高本地底区外环境年γ累积照射量为190.0±46.8mR,对照地区为73.1±20.3mR;高本底地区居民所受年γ累积照射量为330.3±55.1mR,对照地区为103±23.6mR.文中还列出了根据以上数据估算的居民所受年剂量当量,并对有关问题进行了分析和讨论.     

低剂量辐射适应性反应对辐射诱发小鼠胸腺淋巴瘤的影响

目的 探讨低剂量辐射对致癌剂量辐射诱发小鼠胸腺淋巴瘤的影响及其免疫学机理。方法 采用4次1.75GyX射线全身照射C57BL/6J小鼠诱发胸腺淋巴瘤模型, 观察不同剂量照后6个月小鼠胸腺淋巴瘤发生率, 照后1个月脾脏NK细胞毒活性、IL-2和γIFN分泌活性、腹腔巨噬细胞吞噬功能及其TNFα分泌活性以及胸腺细胞分化的变化。结果 每次1.75Gy照射前6h或12h接受25mGy或75mGy全身照射均可降低胸腺淋巴瘤发生率, 且预先接受75mGy全身照射的作用效果更为明显; 每次1.75Gy照射前12h接受75mGy照射小鼠, 上述免疫指标均比单纯1.75Gy照射组增强, 且多数指标接近假照射组; 其胸腺CD4^-CD8^-和CD4^-CD8⁺细胞较单纯1.75Gy照射组减少、CD4⁺CD8⁺细胞增多。结论 低剂量辐射可诱导辐射诱发胸腺淋巴瘤适应性反应, 对致癌剂量辐射诱发小鼠胸腺淋巴瘤有抑制作用, 其抑制作用的免疫学机理可能与低剂量辐射的免疫增强效应及诱导的免疫学适应性反应, 减轻致癌剂量辐射对机体免疫功能的损伤, 使胸腺淋巴瘤前体细胞在形成胸腺淋巴瘤之前被免疫系统清除有关。     

腕式剂量计校准的标准辐射场的建立及其应用

目的 按照国际电工委员会（IEC）技术规范及我国现行核行业标准的相关要求,在国家二级标准剂量学实验室研究与建立用于照射腕式剂量计校准曲线的X、γ射线标准辐射场,使这类监测数据具有溯源性。方法 通过标准剂量仪测量不同能量X射线、¹³⁷Cs及⁶⁰Co参考源等3个辐射场的空气比释动能率,结合相关标准规范提供的弱贯穿辐射H_p（0.07）转换系数,确定了照射腕式剂量计校准曲线的X、γ标准辐射场参考条件,使用热释光腕式剂量计（TLD）在国际标准化组织（ISO）圆柱模体上照射,完成了TLD腕式剂量计线性、能量响应等剂量学指标的验证工作。结果 建立了用于照射腕式剂量计校准曲线的X、γ射线标准辐射场。结论 建立的X、γ标准辐射场可以用于照射腕式剂量计标准曲线和能量响应等特性实验的技术服务、并为开展相关的研究工作提供实验条件,进一步提高了监测数据的可比性和可靠性。     

不同剂量率60Co γ射线照射对人外周血辐射敏感基因表达变化的影响

目的 探讨不同剂量率⁶⁰Co γ射线照射对辐射诱导的基因表达水平改变的影响。方法 ⁶⁰Co γ射线照射3例正常人离体外周血,剂量率分别为0.2、1.0和2.0 Gy/min,照射剂量为0、1、2、4和6 Gy,照射后24 h收集细胞,实时荧光定量（PCR）法对11个基因（CDKN1A、MDM2、PCNA、FDXR、GADD45A、PHPT1、ASTN2、TNFSF4、POLH、GDF-15和PPM1D） mRNA表达水平进行相对定量检测;逐步回归法构建不同剂量率基因组合表达模型。结果 不同剂量率0.2、1和2 Gy/min ⁶⁰Co γ射线照射后,辐射诱导的11个基因的相对表达量随照射剂量增加而升高,具有显著的剂量依赖性（R²=0.744~0.998,P< 0.05）;0.2 Gy/min ⁶⁰Co γ射线照射2 Gy后,CDKN1A、FDXR、PHPT1和TNFSF4基因的表达量明显高于1和2 Gy/min剂量率组,差异具有统计学意义（t=3.73、5.73、2.44、2.77、3.53、2.68、2.43、2.05,P< 0.05）;2 Gy/min ⁶⁰Co γ射线照射6 Gy后,PPM1D基因表达量明显高于其他两个剂量率组（t=3.82、2.54,P< 0.05）;不同剂量率基因组合表达模型由2~3个基因组成,回归方程的R²值为0.951~0.976（P< 0.05）。结论 在0.2~2 Gy/min剂量率范围内,不同剂量率⁶⁰Co γ射线照射可能会影响辐射诱导人外周血基因表达水平的改变。     

用牙釉电子自旋共振方法估算慢性辐射损伤人员的受照剂量

目的 用于牙釉电子自旋共振对慢性辐射损伤人员的受照剂量进行估算的方法。方法 用电子自旋共振仪测定慢性辐射损伤人员牙釉电子自旋共振信号强度，用剂量－效应曲线法和附加剂量法来重建辐射损伤人员的受照剂量，探讨牙釉电子自旋共振法估算受照剂量的可行性；并比较了不同能量的射线（1.25MeV的γ射线和6MeV的X射线）对牙釉电子自旋共振信号强度的影响。结果 用两种方法估算的辐射损伤人员受照剂量基本一致；对能量1.25MeV的γ射线和6MeV的X射线进行比较，无论从剂量－效应曲线的直线系数，还是用混合照射后的剂量估算，两者差别不大。结论 慢性辐射损伤人员的受照剂量可以用于牙釉电子自旋共振方法进行估算，射线能量在1.25MeV-6MeV范围内对牙釉电子自旋共振信号强度影响不大。     

Aspects of retrospective ESR dosimetry (invited paper)

A review is given on the major technological and methodological aspects of retrospective ESR dosimetry with tooth enamel. Topics include the collection and preparation of samples, the evaluation, treatment and interpretation of the ESR signals, and the procedure of dose reconstruction. Two pathways are described to differentiate between doses from different internal and external sources. They are based on dose comparisons as evaluated from different tooth tissues or from dose vs age dependencies obtained by ESR dosimetry from populations with different exposure conditions. The concepts given are illustrated by recently achieved ESR doses that were reconstructed from teeth of radiation workers and members of the public of the Southern Urals region, Russia.     

Application of EPR retrospective dosimetry for large-scale accidental situation.

Above 3000 tooth enamel samples, collected at population of radioactive contaminated territories after Chernobyl accident, the Chernobyl liquidators, the retired military of high radiation risk and the population of control radiation free territories were investigated by EPR spectroscopy method in order to obtain accumulated individual exposure doses. Results of EPR spectra measurements are stored in data bank; enamel samples are also stored in order to provide the possibility to repeat the measurements in future. Statistical analysis of results has allowed to detect the contribution into EPR signal in tooth enamel due to the action of the natural background radiation, and the radioactive contamination of territory. In general, the average doses of external exposure of the population obtained with EPR spectroscopy of teeth enamel are consistent with results based on other methods of direct and retrospective dosimetry. Essential exceeding of the individual doses above the average level within the population groups was observed for some persons. That gave the possibility to detect the individuals with overexposure, which were included into groups for medical monitoring.     

Parameters affecting EPR dose reconstruction in teeth.

The aim of this paper is to analyze the lower limit of detection (LLD), linearity of dose response, variation of radiation sensitivity between different tooth enamel samples, and time/temperature stability of EPR biodosimetry in tooth enamel. The theoretical LLD is shown to be 0.46 mGy, which is far lower than the measured value of about 30 mGy. The main issues to lowering LLD are the differentiation of the radiation-induced component against the total EPR spectrum and the complex nature of the dose dependence of the EPR signal. The following questions are also discussed in detail: need for exfoliated or extracted teeth from persons of interest, accounting for background radiation contribution; conversion of tooth enamel absorbed dose to effective dose; accounting for internal exposure specifically from bone-seeking radionuclides. Conclusions on future development of EPR retrospective biodosimetry are made.     

Tooth enamel EPR dosimetry: sources of errors and their correction.

Some of the most important sources of systematic errors in dose determination using tooth enamel EPR spectroscopy and ways of reducing those errors are discussed. Enamel from the outside of the front teeth should not be used for dose determination because of induction of paramagnetic centers by solar light. The accuracy of the method in the low dose range is limited by variation in the shape of the EPR signal of unirradiated enamel, which can be described by an initial intrinsic signal and which varies for different samples with standard deviation of 20-30 mGy. The energy dependence of enamel sensitivity should be taken into account in the form of a correction factor. The value of this factor is estimated at 1.1-1.3 for real radiation fields in radiation contaminated territories. Variation in enamel sensitivity for different samples is shown to be within limits of 10-15% of the average value.     

牙釉质ESR回顾性剂量技术与剂量重建

电子自旋共振作为一种回顾性剂量测定技术在剂量重建中应用日益广泛。介绍了电子自旋共振剂量估算的基本原理和过程,包括样品的收集和准备、ESR的测量和信号处理、剂量校准、结果的解释、误差来源及新的进展。另外,还介绍了此技术在剂量重建中的一些应用实例。     

ESR and TL dosimetry systems: comparative measurements for human phantom

Mixtures of small fragments on tooth enamel as well as thermoluminescence (TL) dosimeters were placed into the tissue-equivalent phantom of the human head with skeleton (approximately at the level of the jaws) and irradiated using ¹³⁷Cs low dose-rate gamma therapeutic sources (‘SELEKTRON’ LDR ¹³⁷Cs). Phantom, samples of teeth and TL detectors were irradiated behind water tank to produce scattered irradiation. The same irradiation with the same geometry was performed in air too. For gamma-spectrometry ¹³⁷Cs sources with very low activity were used but with the same geometry as therapeutic sources. The absorbed dose in enamel was estimated with the help of ESR spectrometer ‘ESP-300 E’ (Brucker). The samples of tooth enamel were partially used for preliminary dose evaluation by ESR signal before starting of experiment. TL dosimetry was performed by TL reader model 8800 (HARSHAW) using TL dosimeters calibrated with ¹³⁷Cs. The paper presents data obtained in comparative aspects.